Heater element for vane type snap-action devices



Feb. 22, 1966 J. w. WELSH 3,236,973

HEATER ELEMENT FOR VANE TYPE SNAP-ACTION DEVICES Filed Feb. 28 1964"a"... 35 INVENTOR. 2 4 W JAMES M Was/7 BY J 30 W I AT/ZQ/VEVS UnitedStates Patent 3,236,973 HEATER ELEMENT FOR VANE TYPE SNAP-ACTION DEVICESJames William Welsh, Summit, N.J., assignor to Hudson .lLamp Company,Kearney, N.J., a corporation of New ersey Filed Feb. 28, 1964, Ser. No.348,117 3 Claims. (Cl. 200-122) mobile directional signal systems. Sucha vane type snap-action device is described in US. Patent No. 3,088,012issued April 30, 1963.

Vane type snap-action devices generally comprise a vane provided with amotive element ribbon which upon heating and expansion causes the vaneto undergo a snapping-type action. As described in the above mentionedPatent No. 3,088,012, a vane curved about its longitudinal axis isprovided with a high resistance metallic motive element-ribbon weldedacross and held under tension by the vane, such as to stress the vaneabout its vertical axis. In a series type snap-action device, the ribbonis in series with two normally closed contacts, one of which is mountedon the ribbon. When current is passed through the high resistanceribbon, the ribbon heats up and expands, causing the vane to snap and toassume a curvature about the longitudinal axis. Expansion of the ribbonopens the contacts and allows the ribbon to cool and contract, which inturn causes the vane to snap and return to the position in which thecontacts are normally closed.

In parallel type snap-action devices where the contacts of thesnap-action device are normally open, a heating coil is mounted on themotive element ribbon to cause the ribbon to expand and contract,expansion and contraction of the ribbon in turn causing the snap-actiondevice to go through a snap-action cycle.

Heating coils of the prior art have generally been wound around themotive element ribbon itself. It has been found that by providing theheating coil adjacent the motive element ribbon rather than wound aroundit, ease of assembly in manufacturing the sn-ap action device isintroduced while providing superior heating action of the ribbon.

It is thus an object of this invention to provide a new and improvedmeans for heating the motive element ri' bon in vane type snap-actiondevices.

It is a further object of this invention to provide means for heatingthe motive element ribbon of snap-action devices that is easilyassembled and that provides greater concentration of heat to themetallic ribbon.

Other and further objects of this invention will make themselvesapparent from the following description and drawings wherein:

FIG. 1 is a side perspective view of a vane type snapaction deviceshowing it in completed form suitable for installation,

FIG. 2 is a bottom perspective view of the snap-action device,

FIG. 3 is a top cross-sectional view taken along line 3-3 of FIG. 1,

FIG. 4 is a side cross-sectional view taken along line 44 of FIG. 1,

FIG. 5 is an elevational view of one embodiment of the presentinvention,

FIG. 6 is a top partially sectional view taken along line 6-6 of FIG. 5,and

FIG. 7 is an elevational partially sectional view of another embodimentof the present invention.

In general, the present invention contemplates the provision of aheating coil adjacent to the metallic motive element ribbon of a [vanetype snap-action device. The heating coil is comprised of an insulatedwire wound around a metallic strip affixed adjacent to the motiveelement ribbon. One end of the wire is soldered to the metallic strip,while the other end is connected to one of the terminals of thesnap-action device.

More particularly, referring to the figures, the snapaction device isprovided with a base 10 of Bakelite or other non-conductive material.Base 10 is provided with a shell 11 having a peripheral flange 11aadapted to register over base 10, flange being rolled or crimped tosecure shell 11 to base 10 as shown in FIGS. 1 and 2. Base member 10 isshown to have secured Within its terminals 12, 13 and 14. Terminals 12,13, and 14, re-

; spectively, liuve lugs 15, 16, and 17 which are adapted to be insertedinto an electrical socket. As shown in FIG. 4, electriacl terminals 12and 14 are angled as at 17 and 18 within base 10 such as to provide asecure mounting of terminals 12 and 14.

As shown in FIGS. 3 and 4, terminals 12, 13 and 14 have arms 19, 20 and21 extending through the top of base 10. Terminal 12 also has an angledextension member 19a aflixed to arm 19. The angled portion 19b ofextension member 19a is provided with a contact 22. Arm 21 has mountedthereon stressed vane 23. Vane 23 comprises a thin metallic piece ofmetal curved along its horizontal axis to provide a convex front faceand a concave back face. The vane is constructed so that it is adaptedto be bent inwardly against the cu-nvatnre and tend to flatten out whena force is exerted at its side edges 24 and 25.

Ribbon 26, of very thin metal, is attached to vane 23 adjacent its sideedges by electrical spot-welding or the like. Ribbon 26 is preferablymade of a high-resistance metal such as a nickel-chromium alloy whichhas a difterent coefficient of expansion than the metallic vane. Ribbon26 is aflixed to vane 23 in such a way as to stress vane 23 out of itsnormal curvature about is horizontal axis such that the vane is deformedor curved about its vertical axis rather than about the horizontal axis.

'The bottom corners of vane 23 are bent inwardly so that part of theribbon adjacent edges 24 and 25 is bent inwardly. The increased frictioncaused by the bending at the corners of the vane assists in holding theribbon and provides for maximum static pulling force at ambienttemperature. Vane 23 is provided with an electrical contact 27 alignedwith but horizontally spaced from contact 22 of the angled portion 19b.

According to one embodiment of the present invention, mounted adjacentto ribbon 26 is a thin metallic strip 28 which may be affixed to ribbon26 at one end thereof. A heater coil 29 is mounted on strip 28. Coil 29comprises a wire 30, a portion of which is wound around strip 28. Theinsulation of wire 30 is striped from both ends thereof, one end beingsoldered to the free end of strip 28 and the other end being aflixed asby soldering or the like to the free end of metallic arm 31. Ann 31 ismounted on post 32, post 32 being aflixed to element 13 within base 10.

Vane 23 is further provided with shunt wire 33, Wire 33 being affixed atone end thereof adjacent to contact 27 on vane 23 and being aflixed atthe other end thereot to terminal 13 within base 10. Wire 33 is providedto permit the snap-action device to operate in a heavy load circuitwhere the amount of load current would ordinarily burn out the vane ofthe snap-action device.

As shown in FIG. 7, a further embodiment of this invention contemplatescoil 29 being wrapped around a U- shaped member 35, member 35 beingpreferably alfixed near the center of ribbon 26.

As shown in FIG. 3, the snap-action device is provided with threeterminals and thus arm 20 of terminal 13 is connected to arm 19 ofterminal 12 by means of electrically conductive metallic strip 36,terminals 13 and 14 thus being at the same electrical potential. It willbe understood that in a two-terminal snap-action device, terminal 13 andarm 19 would be omitted and that therefore strip 36 would beunnecessary.

In operation, when an electrical potential is impressed across terminals12 and 14, as when a switch is thrown to introduce the snap-actiondevice into an automobile directional signal circuit, current will passthrough high-resistance coil 29 since contacts 22 and 27 are normallyopen. Since coil 29 is made up of a number of turns of high-resistancewire, heat will be produced by the passage of current through coil 29.Since coil 29 is immediately adjacent to metallic ribbon 26,.ribbon 26will be heated by coil 29, the heating of ribbon 26 causing expansionthereof. When ribbon 26 has expanded such that the stresses in vane 23overcome the lessening tension in ribbon 26, vane 23 will undergo asnapping action. Contacts 22 and 27 are then closed, causing current toflow through the circuit of terminal 12, arm 19, extension 19a, angledportion 1%, contacts 22 and 27, vane 23, and terminal 14. When contacts22 and 27 are closed, heater coil 29 is short-circuited, thus cutting011 current flow through coil 29. This allowsribbon 26 to cool andcontract, which is turn causes vane 23 to be snapped back into itsstressed condition. Contact between contacts 22 and 27 is thus brokenand the cycle is repeated as long as the snap-action device is kept inthe signalling circuit.

Shunt wire 33 is provided for use of the snap-action device in a circuithaving high current. Wire 33 shunts the larger portion of the currentpast vane 23, thus preventing burnout of the snap-action device.

It will be understood that since mechanical equivalents will be readilyapparent to those skilled in the art, that this invention is not to belimited to the description and drawings herein but rather by theappended claims.

What is claimed is:

1. A vane type snap-action device comprising a base, a pair ofelectrical terminals mounted on said base, said terminals having armportions extending through the top of said base, a snap-action vanemounted on the arm of one of said terminals, a motive element ribbonfixed across and held under tension by said vane, a pair of normallyopen contacts respectively mounted on said vane and said other terminaladjacent to and opposite each other, a me tallic strip mounted on saidribbon at one point only such that at least one end of said strip isfree and a high resistance insulated heater wire wound around saidstrip.

2. The vane type snap-action device of claim 1 wherein said metallicstrip extends substantially parallel to said motive element ribbon andis affixed at one end only to said ribbon, the other end thereof beingfree.

3. The vane type snap-action device of claim 1 wherein saidstrip issubstantially arcuate and is affixed to said motive element ribbon atsubstantially the central portion of said strip, the two ends thereofbeing free.

References Cited by the Examiner UNITED STATES PATENTS 1,966,444 7/1934Guett 200-116 2,842,642 7/1958 Colombo et a1 200122 3,174,012 3/1965Siiberg 200137 X BERNARD A. GILHEANY, Primary Examiner.

L. A. WRIGHT, Assistant Examiner.

1. A VANE TYPE SNAP-ACTION DEVICE COMPRISING A BASE, A PAIR OFELECTRICAL TERMINALS MOUNTED ON SAID BASE, SAID TERMINALS HAVING ARMPORTIONS EXTENDING THROUGH THE TOP OF SAID BASE, A SNAP-ACTION VANEMOUNTED ON THE ARM OF ONE OF SAID TERMINALS, A MOTIVE ELEMENT RIBBONFIXED ACROSS AND HELD UNDER TENSION BY SAID VANE, A PAIR OF NORMALLY